Dynamic Secondary Ion Mass Spectrometry Research Articles

Characterisation of sub micron salt-doped polymer electrolyte films

We report studies on thin films of a salt doped polymer electrolyte model system. Films of poly(ethylene oxide) with thickness near 1400 Å, doped with lithium triflate salt at salt concentrations ranging from 0 to 40% by weight, were characterised. The high surface to volume ratio of the thin film samples makes them ideal for the study of interfacial effects on the physical properties. The lateral morphology of the system was studied with optical and atomic force microscopy, revealing strong similarities to the bulk system. The composition depth profiles of the ionic species were measured directly using dynamic secondary ion mass spectroscopy (d-SIMS) as well as X-ray photo-electron spectroscopy (XPS) accompanied with ion sputtering. The results are discussed in terms of the possible implications of interfacial effects on practical ionically conducting systems.

The effect of moisture on the fracture energy of TiN/SiO 2 interfaces in multi-layer thin films

The fracture energy of TiN/SiO 2 interfaces, prepared as part of multi-layer structures by conventional thin-film device processing, has been measured using a residually stressed, micro-strip decohesion test. Both the decohesion energy and the decohesion velocity, at fixed strain energy release rate, are found to be affected by the presence of moisture and are functions of relative humidity. A threshold strain energy release rate for interface decohesion in the presence of moisture is determined. Also, the diffusivity of moisture along the TiN/SiO 2 interface, at room temperature, is determined to be (6±2)×10 −13 cm 2/s from sequential images of the 2D concentration profiles formed by dynamic secondary ion mass spectroscopy (SIMS). Evidence is presented indicating that the TiN/SiO 2 interface is weakened by in-diffusion of moisture ahead of the advancing decohesion front.

Deuterium sintering of silicon-on-insulator structures: D diffusion and replacement reactions at the SiO2/Si interface

We use dynamic secondary ion mass spectrometry (SIMS) to examine the mechanism of H (D) incorporation into and retention within a buried SiO2 film at 625 °C. We find that diffusion of H2 (D2) through the Si/SiO2/Si structure at this temperature is facile and that isotopic exchange occurs at the interfaces upon subsequent forming gas anneals at 625 °C. A detailed examination of the isotopic exchange process indicates that the interfaces do not exhibit equivalent behavior. We also describe the artifacts observed in the SIMS profiles by comparing positive and negative secondary ion profiles.

Non-uniform composition profiles in thin film polymeric nanofoams

Neutron reflectivity (NR) and dynamic secondary ion mass spectroscopy (DSIMS) were used to study compositional variations as a function of film depth in thin polymeric nanofoam films formed from triblock copolymers containing 15 wt%, 13 kg/mol polypropylene oxide end blocks with a fluorinated polyimide center block. The triblock copolymer films were spun cast and imidized on silicon substrates and showed an excess amount of polyimide present at both the air/film and film/substrate interfaces. Upon foaming the films showed a slight densification, and the formation of a 50–150 Å thick polyimide skin at the air interface. The final nanofoam materials had a calculated porosity of roughly 20 vol.% in the center portion of the film.

Perovskite lead titanate PLD thin films: study of oxygen incorporation by [formula omitted] tracing technique

PbTiO 3 (PT) films have been deposited by pulsed laser deposition (PLD) technique on polycrystalline platinum substrate kept at a constant temperature of 550°C in a 30 Pa 18 O atmosphere pressure. The fluence and the laser repetition (frequency quadrupled Nd-YAG, 266 nm) have been varied in the range 1.5-3 J cm −2 and 2-10 Hz, respectively. The obtained films exhibit a perovskite structure and have been analyzed by dynamic secondary ion mass spectrometry (D-SIMS) in order to determine the concentration profiles of 16 O (coming from the PbTiO 3 target) and 18 O (ambient gas). The effects of different parameters of the PLD process are discussed, such as the cooling step of the film in oxygen atmosphere after deposition, the laser repetition rate and the gas phase reactions.

Trace Element Microanalysis in Iron Meteorites by Laser Ablation ICPMS

A laser ablation microanalysis system has been developed that can analyze trace elements with a sensitivity in the ppb range, using a CETAC LSX-200 laser ablation system with a Finnigan Element. This capability has been applied to a set of iron meteorites to demonstrate the laser microprobe's analytical capability for the determination of platinum group elements (PGEs) with a spatial resolution of ∼20 μm, comparable to that of dynamic secondary ion mass spectrometry (SIMS). The laser is shown to provide an accurate means of solid sampling for magnetic sector inductively coupled plasma mass spectrometry (ICPMS), allowing the determination of bulk metal composition, chemical zoning within the sample, and depth profiling. Recovery of the chemical zoning in taenite lamellae was achieved for Ru, Rh, and Pd, which was not previously possible using SIMS. The methods presented here show that magnetic sector ICPMS can be successfully coupled to a laser ablation system, providing the advantages of higher sensitivity of the sector instrument, low background count rates (<0.1 counts/s), and flat-topped spectral peaks, while minimizing tradeoff against the speed of data acquisition required to handle the transient signals from the laser ablation system.

Diffusion and Distribution of Photoacid Generators in thin Polymer Films

AbstractDistribution and diffusion of two fluorinated ionic photoacid generators (PAGs) in thin polymer films have been investigated by depth profiling of the intrinsic label elements of both the PAGs and a silicon containing carrier polymer with Rutherford Backscattering Spectrometry (RBS) and dynamic Secondary Ion Mass Spectroscopy (SIMS). Distribution and diffusion of the PAGs in a bilayer film stack, which consists of a thin silicon containing polymer film on top of a thick thermally cross-linked Novolak film on a silicon substrate, have been studied as a function of the Novolak cross-linking temperature. Deposition of the PAG containing polymer films on top of the cross-linked Novolak films by spin coating results in an interphase with enriched PAG. Subsequent annealing of the film stack causes expansion of the interphase and diffusion of the PAG into the underlying Novolak film when Novolak is cross-linked at lower temperatures. On the other hand, there is a uniform PAG distribution and no detectable diffusion of the PAG into Novolak when it is cross-linked at high temperatures. The variations in the PAG distribution and diffusion are attributed to the changes in the chemical and physical properties of Novolak during cross-linking.

Effects of Co-Dopants on the Microstrucutre and El Properties of the Zns:Mn Luminescence Materials

ABSTRACTThin films of zinc sulfide (ZnS) doped with Mn, were deposited using magnetron sputter source. The electroluminescent properties of the as-deposited films were relatively poor. Post- deposition rapid thermal annealing (RTA) with and without co-dopants was studied. Significant changes in microstructure and EL performance were observed on the samples after post-sputter processing. Transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) were employed to characterize the microstructure. Both inter-grain and intra-grain distributions of the co-dopants were measured using energy dispersive X-ray spectra (EDX) and the distribution versus thickness was determined by dynamic secondary ion mass spectrometry (SIMS). A correlation between electroluminescent properties and the microstructure is obtained.

Low-cost modification for the high-frequency raster on the Cameca IMS-3F secondary ion mass spectrometer

The Cameca IMS-3F secondary ion mass spectrometry (SIMS) instrument, now three generations old, is still considered quality surface-analysis equipment. It was designed more than two decades ago, at a time when power transistors were the means of rastering high voltages at high frequencies. In our modification, we have replaced the high-frequency amplifiers with a simple operational amplifier (op amp) circuit that greatly enhances the capabilities of this instrument. In a Cameca dynamic SIMS instrument, the primary ion beam is focused into a small spot (∼5–100 μm) and then is rastered over an area generally between 25 μm×25 μm and 500 μm×500 μm. The raster signal is a sawtooth waveform with separate high and low-frequency components for X and Y, respectively. The transistor design of the raster amplifier does not produce a sharp waveform at high frequencies. Instead, the signal appears rounded at the top and bottom. This, in turn, allows the ion beam to spend more time at the edges of the rastered area, etching the sides at a greater rate, producing the so-called “dog ears” at the bottom of the SIMS crater. Under most analysis conditions, these dog ears are not a problem because the analysis area is much smaller than the rastered area (e.g., a 60-μm-diameter circular analysis area for a 250 μm×250 μm rastered area) and is taken from the center. However, when the sputter depth is great, or the analysis area approaches the size of the rastered area, there is a loss of depth resolution. Another problem occurs when sputtering through thin films deposited on glass or other insulating materials. During depth profiling, as the material is sputtered away, the edges reach the insulator before the analysis area, which causes a charge buildup. The operator must then stop the profile prematurely, resulting in a loss of information.

Behavior of residual stress on CVD diamond films

Diamond films were deposited on a Si substrate with a hot filament chemical vapor deposition (HFCVD). Then the residual stresses in the films were measured by the curvature method. The results showed that the residual stress changed from a compressive to a tensile stress with increasing film thickness. Tensile residual stresses were almost saturated, and those showed higher stress values with increased methane flow rate. We deduced a vacancy and grain boundary acted as a potential source of tensile stress. In order to investigate the effects of hydrogen on the residual stress, qualitative and quantitative analyses were carried out with the dynamic secondary ion mass spectrometry (SIMS) and elastic recoiled detection (ERD).

The effect of surface ion-induced defects on CO adsorption on polycrystalline Ni

CO adsorption on polycrystalline nickel was investigated by dynamic secondary ion mass-spectroscopy at 10−5–10−3 Pa and 300–500 K. An increase of secondary ion currents NiCO+/Ni+ ratio was found in the range from 300 to 350 K, while at T>350 K it decreased sharply. These data were explained by a kinetic model, in which adsorption and desorption of tightly bound CO goes through weakly bound CO formed due to ion-induced defects.

Phase Separation of Polystyrene and Bromo−Polystyrene Mixtures in Equilibrium Structures in Thin Films

Scanning transmission X-ray microscopy (STXM), atomic force microscopy (AFM), and dynamic secondary ion mass spectrometry (DSIMS) were used to obtain the true three-dimensional concentration profiles of polystyrene (PS) and bromo−polystyrene (PBrx=0.79S where x = fraction of monomers brominated) blend films as a function of PBrx=0.79S concentration. Upon annealing, it is found that the PBrS becomes encapsulated by the PS. The encapsulation provides for a continuous PS phase for all blend compositions and explains the observed structures that are formed for different PBrS volume fractions. The encapsulation allows us to estimate the dispersive contribution of the PBrS surface energy to be less than 20.6 dyn/cm.

Dynamics of Polymer Interdiffusion: The Ripple Experiment.

We explore the interdiffusion of oppositely labeled triblock polystyrene chains, HDH/DHD, during welding in the melt using dynamic secondary ion mass spectroscopy (DSIMS) and specular neutron reflectivity (SNR). The HDH chains have the central portion of the chain deuterated (D) approximately 50% while the two ends (H) each have approximately 25% protonation; the DHD is oppositely labeled, but each set of chains contains about 50% deuteration. During welding, the deuterium depth profile exhibits "ripples" whose characteristic features, such as the time and molecular weight dependent shape, amplitude, and position, are very sensitive to the microscopic details of the polymer dynamics. The ripple experiment is especially sensitive to the presence, or absence, of topological constraints and anisotropic motion of chains. The current work significantly extends the molecular weight range up to 400 000. This allows greater separation of the six key ripple features used in deciphering the correct polymer dynamics model at the polymer-polymer interface. The DSIMS and SNR experimental results are compared to theoretical predictions and ripple simulations for Rouse, polymer mode-coupling, reptation (with and without tube broadening), and other phenomenological dynamics models. The six ripple characteristics were found to be perfectly correlated and convincingly consistent with the predictions of the reptation dynamics model. The ripple results are in significant disagreement with the polymer mode-coupling model proposed by Schweizer and other tubeless models. We conclude that the reptation model, proposed by DeGennes in 1971 with parallel developments by Edwards, is the correct model to describe the dynamics of polymer interdiffusion.

Direct Imaging of Trace Elements, Isotopes, and Molecules Using Mass Spectrometry

Abstract Secondary ion mass spectrometry (SIMS) is based upon the energetic ion bombardment of surfaces resulting in in the emission of sputtered particles, including both atomic and molecular ions. The use of mass spectrometric detection provides a highly versatile and sensitive tool for surface and thin film microanalysis. The scope of the technique includes a diversity of analysis modes including: 1. Elemental Depth Profiling (dynamic SIMS), 2. Laterally Resolved Imaging (ion microprobe or ion microscope analysis), 3. Image Depth Profiling (combination of modes 1 and 2 providing 3-D images), 4. Molecular Monolayer Analysis and Imaging (static SIMS), 5. Sputtered Neutral Mass Spectrometry (post-ionization). Much of the early work in dynamic SIMS centered on depth profiling and imaging techniques, with an emphasis on applications to electronic materials. SIMS has made extensive contributions to semiconductor materials science since the 1960's, including the development of new devices and processes, and in failure analysis.

Secondary ion mass spectrometry for quantitative surface and in-depth analysis of materials

Secondary ion mass spectrometry (SIMS) is a technique based on the sputtering of material surfaces under primary ion bombardment. A fraction of the sputtered ions which largely originate from the top one or two atomic layers of the solid is extracted and passed into a mass spectrometer where they are separated according to their mass-to-charge ratios and subsequently detected. Because the sputter-yields of the individual species, coupled with their ionization probabilities, can be quite high and the mass spectrometers can be built with high efficiencies, the SIMS technique can provide an extremely high degree of surface sensitivity. Using a particular mode like static SIMS where a primary ion current is as low as 10−11 amp, the erosion rate of the surface can be kept as low as 1 A per hour and one can obtain the chemical information of the uppermost atomic layer of the target. The other mode like dynamic SIMS where the primary ion current is much higher can be employed for depth profiling of any chemical species within the target matrix, providing a very sensitive tool (∼ 1 ppm down to ppb) for quantitative characterization of surfaces, thin films, superlattices, etc.

SIMS of biomineralized tissues: present trends and potentials.

The technique of dynamic secondary ion mass spectrometry (SIMS) has, during the 1980s, become a firmly established tool in the microanalytical and microstructural characterization of dental hard tissues. SIMS has proved to be outstandingly suited for charting the distributions of most elements, even at extremely low concentrations, in tooth and bone materials. In-depth concentration profiles as well as surface distribution maps of elements have been recorded with excellent (sub-micron) morphologic resolution. In spite of documented success, only relatively few teams, in a handful of countries, are presently engaged, to any significant extent, in conducting tooth or bone research by the application of SIMS. For dental-medical-surgical laboratories, a partial reason for non-communication is a lack of information about SIMS and its particular assets. Another reason may be connected with an essentially groundless reputation, among non-specialists, of SIMS being an exclusive and expensive technique. Among SIMS laboratories, on the other hand, the inertia in tackling biomineralization is partly due to some particular artifacts of analysis, hitherto not generally known and controlled. The present paper briefly sketches the chief principles of modern SIMS, emphasizing factors of special relevance in the characterization of biomineralized tissues. Examples of recent applications are provided. Present procedures and their limitations are discussed, especially with regard to elemental quantification and imaging. Suggestions for relatively simple modifications to existing routines are offered with the aim of enhancing the ease and availability of SIMS in odontological and surgical research.

Researches on Polymer Surfaces: Structure and Dynamics. Surface Structure and Surface Molecular Motion of Solid Polymer Films.

Novel methods for the characterization of polymer surface structure and surface molecular motion have been presented. Scanning viscoelasticity microscopy (SVM) was used in the studies of the surface mechanical properties of polymeric solids. Employing dynamic secondary ion mass spectroscopy (DSIMS) for the depth profiling of the chemical composition of end-labeled polystyrene (PS) film, the end group segregation at the air/solid PS interface was verified. It was revealed that the molecular motion at the surface of glassy polystyrene (PS) was fairly activated, compared with that of bulk one due to the surface segregation of chain end groups. These results indicate that surface glass transition temperature is depressed due to the increase in free volume near surface region. Temperature dependent X-ray photoelectron spectroscopy (TDXPS) was utilized for the characterization of surface molecular motion of symmetric diblock copolymers. The activation of molecular motion at the surface was also confirmed by TDXPS. The two-dimensional mapping of the surface mechanical properties for the polymer blend ultrathin films was carried out on a nanometer scale by using SVM. Composition profile along the thickness direction of polymer blend thin film was also evaluated on the basis of neutron reflectivity (NR).

Analysis of Surface Molecular Motion of Amorphous Polymeric Solids on the Basis of Scanning Force Microscopy and X-ray Photoelectron Spectroscopy.

Surface molecular motions of amorphous polymeric solids have been directly measured on the basis of lateral force microscopic (LFM), scanning viscoelasticity microscopic (SVM) and differential X-ray photoelectron spectroscopic (D-XPS) studies. SVM and LFM measurements of monodisperse polystyrene (PS) films revealed that, in the case of the number-average molecular weight, Mn less than ca. 30k, the surface was in a glass-rubber transition state at room temperature even though the bulk glass transition temperature, Tg was far above room temperature. The active molecular motion at the polymeric solid surface can be interpreted mainly in terms of excess free volume near the surface region induced by the surface segregation of chain end groups, which was confirmed by dynamic secondary ion mass spectroscopy (DSIMS). D-XPS measurement revealed that the surface Tg for the poly(styrene-block-methyl methacrylate) diblock copolymer films increased gradually with an increase in depth from the air/polymer interface.

Dynamic and static secondary ion mass spectrometry studies of the solvation of HCl by ice

H. A. Donsig and J. C. Vickerman, J. Chem. Soc., Faraday Trans., 1997, 93, 2755 DOI: 10.1039/A701724C

Characterization of the noise in secondary ion mass spectrometry depth profiles

The noise in the depth profiles of secondary ion mass spectrometry (SIMS) is studied using different samples under various experimental conditions. Despite the noise contributions from various parts of the dynamic SIMS process, its overall character agrees very well with the Poissonian rather than the Gaussian distribution in all circumstances. The Poissonian relation between the measured mean-square error and mean can be used to describe our data in the range of four orders. The departure from this relation at high counts is analyzed and found to be due to the saturation of the channeltron used. Once saturated, the detector was found to exhibit hysteresis between rising and falling input flux and output counts.